Double-action antenna

Abstract

The invention relates to double-action antenna structures. The structure comprises an antenna inside the covering of a mobile station, a switch (SW) and a whip, element ( 240 ) movable in relation to the former two. The internal antenna comprises two elements the first of which ( 220 ) is connected to the feed conductor ( 202 ) of the whole antenna structure and the second to the signal ground ( 203, 210 ). When the whip element is retracted, the said switch galvanically interconnects the elements of the internal antenna. Thus only the internal antenna functions and the whip has no practical significance. When the whip element is extended, its lower end disconnects, by means of the switch, the elements of the internal antenna, and the whip element itself is connected in series with the first element. Thus, a radiating element is provided by the series connection ( 240, 220 ) of the whip and the first element, and the shorted element ( 230 ) of the internal antenna has no practical significance. The first element further provides for the matching of the whip element. The antenna structure may have one or more operating bands. In the structure according to the invention the length of the whip element may be chosen relatively freely because the electrical length of the structure can always be made suitable by means of the internal antenna element connected in series with the whip element. No mechanical parts or components are needed for the matching of the whip element.

What is claimed is:  
     
       1. An antenna structure comprising a signal ground, an internal antenna of a radio apparatus and a whip element movable in relation to the internal antenna, wherein the internal antenna comprises a first element connected to a feed conductor of the antenna structure and a second element connected to the signal ground, the antenna structure further comprising a switch which, when the whip element is retracted inside the radio apparatus, galvanically interconnects the first and second elements and, when the whip element is extended, disconnects the first and second elements and galvanically connects the first element with the whip element to feed and to match the whip element. 
     
     
       2. An antenna structure according to  claim 1 , wherein the first and second elements are planar elements substantially on the same plane, said internal antenna then being a planar antenna. 
     
     
       3. An antenna structure according to  claim 1 , wherein said internal antenna is a loop antenna. 
     
     
       4. An antenna structure according to  claim 1 , wherein said switch comprises a contact spring attached in a fixed manner to the first element and a counter contact in the second element. 
     
     
       5. An antenna structure according to  claim 1 , wherein the extended whip element together with the first element is arranged to resonate substantially at least at one same frequency as the internal antenna. 
     
     
       6. An antenna structure according to  claim 1 , wherein the first and second elements are rigid conductive elements. 
     
     
       7. An antenna structure according to  claim 1 , wherein the first and second elements are conductive areas on a surface of a dielectric board. 
     
     
       8. A radio apparatus having an antenna structure which comprises a signal ground, an internal antenna of the radio apparatus and a whip element movable in relation to the internal antenna, wherein the internal antenna comprises a first element connected to a feed conductor of the antenna structure and a second element connected to the signal ground, the antenna structure further comprising a switch which, when the whip element is retracted inside the radio apparatus, galvanically interconnects the first and second elements and, when the whip element is extended, disconnects the first and second elements and galvanically connects the first element with the whip element to feed and to match the whip element.